The project proposes to continue the study of perceived orientation by means of four approaches: 1 - Body-object invariance. Mathematical functions were developed relating body location to object location for depthwise (fore-aft) tilts as well as for lateral (right-left) tilts, analogous to the size-distance invariance hypothesis. It is proposed that the invariance principle of orientation may account for the constancy of perceived object orientation. Additional related studies entail (a) the measurement of apparent body orientation under conditions of body tilt in the frontal and median planes, (b) the photographic measurement of the doll reflex, i.e., the reflexive ocular rotation associated with fore-aft body tilts, (c) determining the role of eye movements in orientation constancy. 2 - Relational determinants. These refer to the main lines of the visual field which may serve as a frame of reference for the orientation of objects as well as of the self. 3 - Egocentric orientation. Reference is made to the perceived orientation of objects with respect to the self in contrast with orientation perceived as relative to the direction of gravity. 4 - Adaptation to optically rotated visual fields: The effects of adaptation upon object and body localization; the isolation of variables relevant to the acquisition and retention of adaptation; the effects of adaptation upon the apparent direction of gaze; the isolation of the locus of adaptation effects.